Study Assesses PET Agent for Detecting Pelvic Lymph Node Metastases in Patients with Prostate Cancer

For patients recently diagnosed with prostate cancer, the emerging positron emission tomography (PET) agent 18F-rhPSMA-7.3 reportedly has a 96 percent specificity rate for detecting pelvic lymph node metastases, according to Phase 3 study results recently presented at the 22nd Annual Scientific Meeting of the Society of Urologic Oncology (SUO).

While conventional imaging and procedures have limitations in the assessment of pelvic lymph node metastases in people with prostate cancer, new research suggests that an investigational positron emission tomography (PET) agent may be beneficial in this patient population.

In a Phase 3 trial of 296 patients recently diagnosed with prostate cancer, researchers assessed use of the prostate-specific membrane antigen (PSMA) agent 18F-rhPSMA-7.3 (Blue Earth Diagnostics/Bracco Imaging) with PET imaging prior to the patients undergoing radical prostatectomy and pelvic lymph node dissection (PLND).

According to a recent presentation of study results at the 22nd Annual Scientific Meeting of the Society of Urologic Oncology (SUO), researchers found that 18F-rhPSMA-7.3 had a 96 percent specificity rate (217 of 226 patients) for detecting pelvic lymph node metastases. The study authors also noted that 18F-rhPSMA-7.3 had a sensitivity rate of 24 percent, a finding that is “consistent” with sensitivity rates reported with other PSMA-targeted radiopharmaceuticals.

Brian F. Chapin, M.D., a co-author of the study, suggested that PET imaging with 18F-rhPSMA-7.3 may provide additional clarity with the staging of people with primary prostate cancer.

“Up to 25 percent of patients with primary prostate cancer may have detectable pelvic lymph node metastases, which are correlated with a risk for recurrence and associated overall survival,” noted Dr. Chapin, an Associate Professor in the Department of Urology in the Division of Surgery at the University of Texas MD Anderson Cancer Center. “Conventional imaging techniques, such as (magnetic resonance imaging and computed tomography), are limited in the information they may provide. Pelvic lymph node dissection (PLND), or pelvic lymphadenectomy, is considered the gold standard in assessing pelvic node lesions, but its use is limited to the planned surgical area. An ideal staging technique for detecting metastatic prostate cancer should include both pelvic nodes as well as more distant soft tissue and skeletal findings.”

The researchers also noted no serious adverse effects with the use of 18F-rhPSMA-7.3. While the study authors noted a 7.9 percent incidence of adverse events that may have been attributed to use of the imaging agent, they noted that injection site pain was the most reported adverse event in 0.8 percent of the study participants.

(For related content, see “Could an Emerging PSMA/PET Imaging Agent Improve the Detection of Recurrent Prostate Cancer?” and “Can MRI-Based Prostate Cancer Screening be a Viable Alternative to PSA Testing?”)